Goddess on the mountain top
Burning like a silver flame
The summit of beauty and love
And Venus was her name
–Shocking Blue/Bananarama

Is Venus dead? Maybe not.

First, a way cool picture:

[Click to hugely embiggen. Note (added February 11, 2012): the vertical scale is exaggerated by 30x to show features more clearly.]

That’s Idunn Mons, a mountain on Venus as radar mapped a few years back by the Magellan space probe. The color overlay is a brand spanking new thermal (temperature) map using an infrared detector on the European Venus Express probe, currently orbiting our sister planet. Red is warmer, and as you can see, Idunn appears to be trying to tell us something.

But what’s it saying? OK, here’s the back story:
If you needed to write a compare-and-contrast essay about Earth and another planet, you could hardly pick a better one than Venus. It’s a lot like the Earth: it has almost the same diameter (12,100 km versus Earth’s 12,740), it possesses about the same mass (5 versus 6 x 1024 kilos), it orbits the Sun a bit closer in than we do (109 million km versus 147). The total carbon content of the planet is similar to ours, too.

But it’s also a lot different. While ours is locked up in the oceans and rocks, Venus has all of its CO2 in its atmosphere, which has caused a runaway greenhouse effect. The pressure at the surface is 90 times ours, and the surface temperature is 460° C (almost 900° F). It’s an alien planet, in every sense of the word.

We also thought it was dead, geologically speaking. Despite showing mountains and other interesting features, maps of Venus indicate that the surface hasn’t appeared to change much over geologic times. We have a pretty good grasp of how its atmosphere works, and the weathering processes it subjects the surface to — which is not be to be trifled with, since the air there is laced with sulfuric acid and a hint of fluorine and chlorine compounds, too. According to all that, the surface looks to have been pretty stable for quite some time.

But that idea might be changing. New studies indicate Venus may have been volcanically active in the recent past, and may indeed still be active!

The atmosphere of Venus is opaque to our eyes (and highly reflective, which is why Venus looks so bright to us from Earth), but the VIRTIS instrument — which stands for the Visible and Infrared Thermal Imaging Spectrometer — on Venus Express was specifically designed to peer through the muck and look at the planet’s surface. It can see temperature differences on the ground there, and when scientists studied the maps, they found several spots where the surface appears to be slightly warmer than you’d expect.

And very interestingly, at least some of these spots on Venus are also associated with raised features (0.5 to 2.5 km (.3 to 1.8 miles)) above the average surface height — mountains, or, perhaps, volcanoes.

The image at the top of this post shows one such area, which is clearly a mountain of some kind in the Imdr Regio area of Venus. The surface on the top of the mountain is a few degrees warmer than the area around it, suggesting the existence of a hot spot under the surface. It’s very hard to look at that and not think it’s a volcano with a magma chamber under it. The data also indicate flow features that are much less weathered than expected, and therefore most likely very young.

How young is young? According to the team of scientists who took this data, this indicates that Venus was geologically active no more than 2.5 million years ago, and these features may have formed as little as 250,000 years ago! That’s very young indeed when talking about the geologic clock of a planet — that’s more recent than the last Yellowstone eruption in the American northwest, for example. And the fact that the hot spots are still around is a strong indicator that activity is still present on Venus.

Of all the planets in the solar system, Venus gets closest to Earth — it can be as little as about 40 million km (24 million miles) away, compared to Mars which can only get as close as 55 million km (33 million miles). Yet we know less about Venus than Mars. There are many reasons: Venus never strays far from the Sun in the sky, making it more difficult to observe than Mars, and as mentioned above its atmosphere is opaque.

But it’s very much worthy of our study. Why did Venus suffer such a catastrophic runaway greenhouse effect? Why is its surface apparently pretty much all one age (except for this new result)? Why are there hot spots, and are they like ours here on Earth?

Studying the Earth is obviously an incredibly and critically important job for science. And as much as we learn studying it, we need other examples of planets to help us test our ideas. When I was a kid in middle school, I hated having to write those compare-and-contrast essays. But as a scientist — and as a human living in a thin habitable bubble on a planet we have barely begun to understand — I know we need them desperately.

Out of curiosity, how does the temperature of the surface of Venus compare to the temperatures of some of those recently discovered extrasolar planets with extremely-close-to-their-star orbits? I’m wondering if Venus might just be the hottest known place in the universe that’s not the surface of some kind of star.

I know it’s mentioned in the Idunn Mons link, but I think you need to point out up front that the topography shown is highly (30x) vertically exaggerated (as are the majority of depictions of Venus’s surface).

Venus is a very “flat” planet, but the CG flyovers of it invariably stretch the hell out of the relief to make the features stand out. Unfortunately, it gives a lot of people a very, very wrong perception of Venus’s topography!

Flat may not look as sexy as soaring peaks and yawning chasms. But it’s interesting in and of itself, because it teaches us something important about our “sister” planet’s past.

Venus never strays far from the Sun in the sky, making it more difficult to observe than Mars,

But it is a lot brighter, indeed at magnitude minus 4 (when at maximum) it is the brightest of all the planets & the famous Morning &* Evening Star – a.k.a. Hesperus & Phosphoros if memory serves.

Thus Venus one of the easiest objects to recognise in the sky and the brightest object in our sky after our Sun & Moon – excluding the occassional very rare bright supernova, nova or great comet. Albeit it is only in the sky around dusk and dawn. Venus even upstaged Napoleon once when the little French Emperor with the eponymous complex was giving a speech.

Why did Venus suffer such a catastrophic runaway greenhouse effect?

Because its *much* closer to the Sun I reckon. No?

Why is its surface apparently pretty much all one age (except for this new result)?

The theory I’ve read is that the Cytherean crust is much thicker than Earth’s and thus traps the heat inside. There are no plate tectonics but the heat builds up underneath until a major volcanic episode occurs – planet-wide!

Venus lacks plate tectonics I think although it does have continents (Aphrodite Terra & Ishtar Terra) but then volcanic hot spots on Earth eg. Hawaii, Mt Gambier & Mt Schank which I’ve just visited in Australia may be unrelated to plate tectonics and something quite different.

Is it possible that the Temperature differential is because of Altitude above Venus’s mean surface Level. I know there is a temperature inversion on Earth (temp reducing with Altitude) but in a runaway ‘greenhouse’ atmosphere, would it be right to expect a temperature inversion?

Norm (#2) From http://www.public.asu.edu/~sciref/exoplnt.htmTau Bootis, which is a star similiar to our sun, has been observed 19 times for doppler velocity perturbations. The time span for these measurements extend from 1995 through February 1996. Based upon these observations it has been determined that Tau Bootis has a planetary companion. Calculations seem to imply a companion with a mass of 3.87 times the mass of Jupiter orbiting its star at a distance of 0.0462 astronomical units. Its orbital period around Tau Bootis seems to be every 3.312 days. In addition, the radius of the companion is considered to be about 1.2 times the radius of Jupiter with a derived temperature of 1,400 K.
1400 K is about 1100 C, so well above Venus.

Actually in the accretion disk around a black hole and centers of stars, temps can get up on the order of millions of Kelvin.

Out of curiosity, how does the temperature of the surface of Venus compare to the temperatures of some of those recently discovered extrasolar planets with extremely-close-to-their-star orbits? I’m wondering if Venus might just be the hottest known place in the universe that’s not the surface of some kind of star.

Venus is nowhere near as hot – it gets as hot as an oven there but not much hotter whereas exoplanets of the Hot Jupiter and “Luciferean” types can exceed a thousand degrees.

Notable examples of this are :

1. HD 80606 b The “Icarus planet” or “Comet orbit Planet” : The most eccentrically orbiting exoplanet discovered in 2009. “HD 80606b is a gas giant planet four times the mass of Jupiter that orbits a star 190 light years from Earth. The planet’s orbit is incredibly elliptical and brings in right up to its Sun for a good scorching at regular intervals.

2. HD 209458 b or “Osiris” : So hot its atmosphere is boiling away so that it may actually resemble a gargantuan comet of sorts! In 1999 this became the first Hot Jupiter found by the transiting technique – detecting a transit of the planet like transits of Mercury & Venus in own solar system and it was the first to have atmosphere detected – a huge cloud of hydrogen and sodium was found to be “boiling” off this exoplanets surface. This led to its nickname by astronomers of “Osiris” after a dismembered Egyptian God. HD 209458 b is located in Pegasus 150 light years away and circles its star every 3.5 days.

3. TrES-4 “Balsawood planet” : Discovered in October 2007, this Hot Jupiter is (was?) the record-holder for largest diameter being 70 % larger than Jupiter’s radius but with a density of just 0.2 grams per cubic centimeter making its density equivalent to balsawood and thus less dense than Saturn. If there was an ocean big enough to float this planet –like Saturn would do so. It would also sizzle being around, 1,330 degrees Celsius (1,600 Kelvin) from orbiting its star in 3 and half days. It was discovered through transiting and directly measured by a team from the Lowell Observatory as part of the Trans-Atlantic Exoplanet Survey (hence TrES) and presents a problem for the theorists being much larger than current models can explain. The Balsawood planet is 1,400 light years distant.

4. HD 183733 b : The first exoplanet where water has been detected – albeit only superheated water vapour in the atmosphere of a HotJupiter! Around August 2007 a team of astronomers led by Giovanni Tinetti used the Spitzer infra-red telescope to study this exoplanet located 64 light years away and found it’s atmosphere was absorbing starlight at key wavelengths indicating water vapour was present. HD 189733 b is a transiting HotJupiter practically scraping the surface of its star as its “year” is a mere 2.2 days! Hints of water were earlier suggested bit less strongly from previous studies of HD 209458 b or “Osiris.” HD 189733 b was also roughly mapped and found to have a massive hotspot on its surface twice the size of Jupiter’s Great Red Spot lying 30 degrees from the sub-stellar point directly facing its sun and baking at a sweltering 925 degrees Celsius. This suggests powerful winds redistribute the heat through the cloudtops and this is backed up with the high temperatures on this exoplanets night side of 650 degrees Celsius – a day-night difference of 260 degrees.

& finally :

5. HD 149026 b : Another transiting Hot Jupiter recently studied (mid 2007) by Spitzer and found to be not only the hottest exoplanet but also the blackest – blacker than charcoal! This is based on its extreme temperature of 2,040 degrees Celsius requiring lost of heat absorption and minimal heat reflecting. That temperature was calculated by measuring its infrared light taken by comparing the stars IR output before and during transits. HD 14926 b has 70-90 times the mass of Earth and orbits a star just a smidgin more massive than our Sun.

Venus by contrast has a surface temperature of 460 degrees Celcisus or 735 degrees kelvin and is the hottest planet in our solar system. (http://en.wikipedia.org/wiki/Venus )

A major difference between Venus and Earth has not been discussed here yet – Venus lacks a large moon. Along with tides, I believe our moon gradually strips our atmosphere. If Venus had a similar large moon, its atmosphere would be thinner.

The hot-spot seems to be on one side of the volcano – not centered on it. Furthermore,
we have a very dense atmosphere and some very strong and persistent winds. Could this just be described by heating from the wind being (adiabatically) compressed when running into obstacles like this one (it seems like the same thing is observed for other “bumps”)?
I haven’t been able to find a temperature map covering a larger area, to challenge my
idea, but I guess I need a little more data to be convinced of recent volcanic activity.
– Regner

Your hypothesis confirm my point (in #8): This “bump” is, in reality, a very small deviation from the surrounding terrain (contrary to the way it appears in the image), and thus you wouldn’t expect a very dramatic adiabatic compression. But the exaggerated vertical relief misleads!

I think these “stretched” depictions should always be presented with an obvious “30x vertical exaggeration” clearly stamped along the bottom in big, friendly letters to avoid reinforcing a false intuition about Venus’s topography. And, pretty please, could someone make a CG flyover with the terrain depicted without vertical exaggeration, just to show how dramatically flat (if that’s not an oxymoron) Venus really is?

I started out mentioning Carl Sagan’s 1960s proposal of seeding the atmosphere with algae and why it won’t quite work since we know more about the planet now. (But the idea of gradual changes in steps through chemical alterations is still very interesting.) The topic got occasionally sidetracked by people saying Mars is a better terriforming candidate (um, the thread was about Venus, so please start a Mars thread,) and a “Floating Cities” contingent who basically ignore the tremendous pole to pole turbulence in the upper atmosphere and seem to be unconcerned about sulfuric acid, etc., but by and large there are some interesting ideas and conjectures, some serious and some humorous on how to transform Venus into a tropical Tahiti planet. (Hint: Its very very hard to do.)
P.S. Somewhere in that thread I linked to information about a paper on how Venus’s volcanism might be a very recent unstable development.

@Chris A. (# 17): I read your post (#4) before writing mine – and I completely agree with you, that the vertical exaggeration should always be mentioned explicitly – it usually is in the original text, but is promptly lost by the first one who quotes it – the sloppiness of media these days. I also agree that no-vertical-exaggeration versions of pictures and animations should be available in parallel. It is also worth noting that for most places of our own planet, a no-vertical-exaggeration fly-over at a similar altitude would be rather less than highly exhilarating.
That said, the compressional heating should still be tested (if it hasn’t already been done) – it is easy if you have the topography and some approximate wind speeds, together with this temperature map. Hmmm, I thought the winds were gale-force, but that is apparently only at the top of the atmosphere – at the surface the wind speeds are only about 0.3 – 1.0 m/s (light air – slower than light breeze)… The 50 times higher density and 92 times higher pressure should still account for something, though. And the 0.5 to 2.5 km tall “bumps” are not utterly insignificant – I believe we wouldn’t call them molehills if they were found on Earth, after all.
– Regner

John @24:
Venus receives 1/4 the solar energy that Mercury does yet the planet is hotter that the sunward side of Mercury. The Earth gets roughly 1/2 the energy that Venus does yet the temperature on average is close to 0C. So … whatcha think – the atmospheric makeup of Venus might just be a factor?

Estimates put the amount of solar radiation reaching and heating the surface of Venus at around 10%. Some 10% is absorbed by its atmosphere. Remainder is reflected back to space. Yup, looks like a potent cocktail of greenhouse gasses keeping her hot. CO2 gone mad.

Light’s intensity falls off with the square of the distance. Using 0C or 273K as the average temperature of the Earth, we multiply that by the square of the distance from Earth to the Sun, about 150 million kilometres, and divide by the square of the distance from Venus to the Sun, about 110 million KM.

This back-of-the-envelope calculation suggests Earth would be around 527K, or 254C, if it were in Venus’ orbit. Since Venus proper is about 490C or 763K, it’s about 200 degrees hotter than we’d expect from solar heating. That dense CO2 atmosphere might be contributing something….

You seem a little rusty in your Science knowledge, since the above is usually taught in High School. It might be time for a refresher course.

Yes, and it should be about 30% warmer than earth, in other words, 30% of the temp diff between zero Kelvins and OUR average temp due to solar heating alone of 273 Kelvins(zero degrees C). So W/O an atmosphere, Venus should average about 354 Kelvins (81 degrees C), not 723 Kelvins (450 degrees C).

I think however, your estimate of 30 % is a bit low. Should be closer to 37%. Adjust figures accordingly.

One question I have never seen answered: How much does Venus’ sloooow rotation affect temperature? Does staying for the equivalent of entire Earth weeks under the relentless Sun elevate the planet’s temperature in its early history to a point where the CO2 runaway got started? How does it affect the temperature situation now?

Steve (31) has it right, but a better transliteration of the name would be I(dh)unn with the dh representing the voiced th sound in the word ‘the’ as opposed to the unvoiced th in ‘thin’. If I remember my Viking age Class from UCB from long ago, she kept the apples of eternal youth.
J. Earley

I liked Chip’s @19 notion of terraforming Venus. Maybe the carbon sequestration technologies we are developing now can be used for that purpose in the far future.

Anyway, the thing that I remember most about Venus comes from the Soviet Venera missions. It’s hard to get a sense of the heat and density of the atmosphere at the surface of Venus until you read about these missions. Can you imagine jettisoning your parachute 50 km above the Earth’s surface and still have a soft landing?

It is theoretically possible to terraform Venus but why would we to? By the time we are technologically able to do that, we would have to already have a solar system wide civilization (Dyson, Type II), and the vast majority of earth type life would be in manufactured space colonies. Living on a planetary surface limits us to the available surface area and a deep gravity well. One such planet as Venus could be disassembled to make millions of space colonies supporting trillions of living entities, all with ready access to the resources of an entire solar system.

Long before we are ABLE to terraform a planet, we’ll have decided it’s superfluous.

Far easier to just BUILD what we want in space, wherever we want them.

Earth sized planet so no microgravity bone loss. Pre-sterilized so no danger of infestation. A world full of untouched resources. Nearest planet and our species already has experience with altering an entire planet’s atmosphere. Plenty of water out there if you’d like to add an ocean or two. Well past time for Terraforming Venus.

“She’s 30% closer to the sun that we are and you think she’s warmer because of CO2?

You have lost it completely.”

You can’t be serious, surely? If you think that distance to the Sun is the sole contributing factor to a planet’s surface temperature, then ask yourself why Mercury is cooler than Venus, despite being almost twice as close to the Sun as Venus is on average. Could it be the CO2 atmosphere of Venus, or am I losing it?!

The high surface temperature on Venus is due to adiabatic compression in the turbulent atmosphere.

The pressure at the surface of Venus is about 90 times that at the Earth’s surface. Venus has enormous winds that cause gas to rise and fall in altitude. As the gas changes height, the pressure changes, and the gas expands or is compressed. When a gas is compressed, its temperature increases. This creates a massive temperature difference between the top of the atmosphere and the surface.

Venus is closer to the sun, but reflects more light, so absorbs slightly less energy than the Earth. The visible surface is the top of the clouds, which approach radiative balance between the incoming solar radiation and the outgoing longwave radiation to space, are relatively cool. The temperature at an altitude where pressure is about 1 Earth atmosphere is actually remarkably Earth-like. But the clouds are about 50-80km above the surface, and compression warms the gas at about 8C/km of altitude (the ‘adiabatic lapse rate’) so the surface is about 400-640C hotter.

The references to a “runaway greenhouse effect” are actually to Venus’s ancient history. It is believed that several billion years ago Venus was like Earth, with a thin atmosphere and oceans on the surface. But somehow all the water disappeared, the carbon locked up in water-related carbonates was released again, and turned Venus into what we see now. This process is thought to be the “runaway greenhouse” – basically, the oceans boiled.

The present day temperature on Venus is easy to explain, and has relatively little to do with CO2 being a greenhouse gas. It’s simply that Venus has a much thicker atmosphere, and high level near-opaque clouds.

OK, I’m very far from being any kind of astronomy expert, but I was always under the impression that Venus was considered to be *very* volcanically active. The thought being that every few hundred thousand years or so it pretty much renews the entire surface – thus explaining why it appears to be so completely featureless.

“published in 1976 by Billy Meier… It was corroborated in October 1975 and August 1976 by information obtained by probes from the US and the USSR. ”
Unfortunately only proof would be publishing book significantly before august 1976, or even before october 1975.

“29th Contact, July 7, 1975”
Ever heard about post-dating?

11 april 2010 I can wrote on computer about crash in Smolensk, date it “8 april 2010”, publish it today and bask in glory of clairvoyancy. So only proof is date of publication.

But all of it is moot, because Venus was explored significantly earlier.http://en.wikipedia.org/wiki/Venus#Exploration
“Mariner 2 mission… on December 14, 1962… passing 34,833 km above the surface of Venus. Its microwave and infrared radiometers revealed that while Venus’s cloud tops were cool, the surface was extremely hot—at least 425 °C”

http://en.wikipedia.org/wiki/Observations_and_explorations_of_Venus#Flybys
“# In 1967, Venera 4 became the first probe to send data from within Venus’s atmosphere. At about the same time, Mariner 5 measured the strength of Venus’s magnetic field.
# In 1974, Mariner 10 swung by Venus on its way to Mercury and took ultraviolet photographs of the clouds, revealing the extraordinarily high wind speed in the Venusian atmosphere.”

Last but not least: some of things that you cited was NOT corroborated. For example point 117 (“But completely other forms (of life) do exist”? Yeah, riiight).

The reason the Venusian crust is so thick is because it doesn’t contain water, so the viscosity of magma is much higher (water acts as a diluent to lower molten silicate viscosity). I think that the reason there is no water on Venus is because there is no life.

When Venus started out, it very likely was like Earth and very likely did have plate tectonics. On Earth, when surface gets subducted, the volatiles are recycled as gases to the atmosphere by volcanoes that surround the subduction zones.

In silicate melts, water acts as a diluent and lowers the viscosity. Water also acts to increase the density of a silicate melt. I think this increase in density is what drove all of the water on Venus into the mantle. As sediments are subducted, silicate melt with the highest density will move down. If that silicate melt has water in it, the water is moved to the mantle and lost.

On Earth, there was life early on, so the subducted sediments also contained free carbon. At high temperatures, water and carbon form methane, which is a gas and which will phase separate from silicate melts and move up as bubbles. I think it is the presence of carbon in Earth sediments which prevented the loss of hydrogen to the mantle.

The conventional thinking is that Earth’s atmosphere became oxic due to the loss of hydrogen into space. I think that is not correct. I suspect that as photosynthesis generated O2, it also generated carbon and also formed the large banded iron formations of Fe2O3 as soluble ferrous iron was oxidized to insoluble ferric iron. I suspect that when the carbon and Fe2O3 were subducted, the Fe2O3 was reduced to liquid metallic iron. Liquid metallic iron would separate out as a separate phase from silicate melts, and being much denser would migrate down. The gas generated (carbon monoxide) would migrate up, recycling the C and O to the atmosphere while the reducing equivalents of that carbon were carried down by the liquid iron.

If this idea is correct, then a possible way to terraform Venus would be to take surface iron oxides, make metallic iron, releasing O2, dissolve carbon in that metallic iron and inject that metallic iron at hot spots like this volcano. As the liquid iron moved down, and encountered water containing silicates, methane would form and move the hydrogen up to the surface. Once there is enough water in the atmosphere, CO2 starts coming out as carbonates.

You would probably want to specifically start up plate tectonics by injecting water (or carbon containing iron) at specific places. Water in the magma would greatly reduce viscosity and facilitate convective flow.

Note that the change in temperature is with the reciprocal of the square root of the distance, not the recip. of the square of the distance. Using an albedo of .9 and an orbital radius of 1.08×10^11m and a solar temperature of 5778, I’m getting a blackbody equilibrium temp of 184K. Interestingly, NASA estimates the same blackbody temp:http://nssdc.gsfc.nasa.gov/planetary/factsheet/venusfact.html

Given Venus’s albedo, even though it’s closer to the sun, it should be far cooler than Earth!

I didn’t expect that. Crap on a cracker!

Venus’s temperature (730K, far above the 184K calculated for a blackbody) has nothing to do with the adiabatic compression. It’s in equilibrium, and so the much greater temperature is due to the “greenhouse” gases in Venus’ atmosphere.